1. Field of the Invention
The present invention relates to paging systems.
2. Description of the Prior Art
Paging systems are in use throughout the world. There are paging systems which transmit pages from satellite transmitters to different cities. An example of such a system is that operated by National Satellite Paging which transmits only pages consisting of numeric characters. A system operated by Metrocast transmits pages to any city within the system through a serial communication link between the cities. The Metrocast system has a central switch which includes all of the subscriber files and a plurality of local switches which are located in separate geographic locations that are connected together by the serial communication link. In the Metrocast system, pages transmitted locally by a single paging service are exclusively made by calling into the city where the page is to be made by a local telephone call. A page to be made on a regional basis involving transmission of pages between two or more locations is called in by an 800 number telephone call to a central facility in San Diego from which the page is transmitted to the city where the page is to be broadcast by the serial communication link. The page is received from the communication link at the city where it is to be broadcast and then broadcast locally by an existing paging service to transmit the page to the person to be paged. In the Metrocast system, the pages are transmitted from the central switch with an address of a switch in a remote location which is to receive the page. All of the intermediate local switches between the central switch and the remote switch which is to receive the page function to relay the pages to the remote switch. The pages are transmitted in on direction along the serial communication link which functions as a loop beginning and ending at the central switch. Each intermediate switch located along the serial communication link removes pages which are addressed to it. However, the intermediate switches do not disassemble the pages and reassemble the pages and add pages thereto originating at the intermediate switches for transmission to other switches along the serial communication link.
BBL Industries manufactures a digital linking module which connects multiple switches together to form a regional paging network. This system transmits individual pages between the switches over a dedicated communication link. The subscriber file is located at the switch originating the page. The remaining switches function only to remove pages which are addressed to them and do not modify the pages. Pages must be originated by calling the switch with the subscriber file.
Paging systems currently in use in the United States maintain subscriber identification information used for making pages transmitted between multiple switches at a single location. In Metrocast, the central switch in San Diego stores the subscriber information in a file which includes the destination(s) of pages for each subscriber. Local paging services which service a single area also maintain a subscriber file at a central location.
Subscriber files contain a subscriber identification number which is a unique identification of the subscriber within the system, whether national or local in nature. The subscriber identification number also functions as the address of the paging receiver of the subscriber and is broadcast with each page that is addressed to the paging receiver of the subscriber. Furthermore, the subscriber file stores the type of service that each subscriber is to have provided when the paging service receives a request for a page. Paging systems rely on the subscriber file to provide the information necessary to provide the type of service that each subscriber requires upon receipt of a request for a page and do not require the requester of a page to know anything other than the identification number of the party being paged and the page itself.
Currently, subscriber files do not store subscriber identification numbers which have a geographic significance regarding the location of the subscriber local paging service within an overall system. Moreover, current paging systems do not process the subscriber identification number to determine a subscriber local paging service location which stores the subscriber file of the subscriber when pages are made which originate outside of the area of the subscribers' local paging service. Current paging systems do not transmit requests for pages originating outside the local paging service providing local service to the subscriber to the local paging service to determine the type of service and the destination of the page by using the network to transmit the request to the local paging service. To place a page from a geographic area outside of the subscribers' local paging service area, current systems require an 800 type call (Metrocast) or a long-distance phone call to be made. Current paging systems do not permit a local call to be used for originating a request for a page from outside the service area of the local paging service, such as requesting a page in Washington, D.C., while being located in New York by making a local phone call to a location in New York.
To date, there is no existing national paging system which substantially covers the geographical United States with reliable service. Because of the cost of hardware, a system like the Metrocast system is not economical in small cities or rural areas where the paging volume is relatively low. Accordingly, while the objective of achieving nationwide paging has been attempted for many years, no existing system integrates local and national paging substantially throughout the geographical United States or throughout the world. The vast majority of paging systems operate totally locally with each system having a limited functionality because of their inability to effectively deliver regional or national (non-local) paging.
Most paging receivers are tuned to receive only a single channel which inherently limits their usage at times when heavy paging conditions exist in a local paging system and further prevents usage in other geographical locations where other channels are used.
Typically, each existing paging system has unique specifications which prevent operation of its paging receivers in other systems. For example, the paging receiver identification codes are not universal. Furthermore, existing paging receivers only receive pages from a single type of transmitter (analog or digital). As a result of paging receivers differing in design and operation, the cost of paging receivers is higher as a result of smaller manufacturing volumes than would be realized if a single paging receiver was usable for a worldwide network.
Paging services which provide a service area that is not limited to a local paging service area (pages involving more than one switch) transmit on a single channel or cyclically on a band of closely related channels.
It is estimated that 25% of the paging receivers in use in the United States are serviced by private paging systems and services (non-common carrier). The private municipal paging system 384, private hospital paging system 386, stock quote service 388, and other private systems 374 illustrated in FIG. 28 are representative of the prior art private paging systems and services. These prior art systems and services have not been integrated with common carrier local paging services as illustrated in accordance with the present invention in FIG. 28 or into a paging network as illustrated in accordance with the present invention in FIG. 1. Paging receivers encompassing both private and common carrier multiple paging frequencies have not been available to date. The transmitters of non-common carrier systems and services have lower broadcast power than the transmitters of common carrier paging systems, and therefore have a limited range in comparison with common carrier systems. As a result, there is a lack of continuity in service range provided by non-common carrier systems and services when a comparison is made to common carrier local paging services. Moreover, the lack of continuity in the range of service provided by private paging systems and services causes persons wishing to receive paging service from common carriers and private non-common carrier systems and services to carry multiple paging receivers creating at least an inconvenience for the user and additional expense in purchasing multiple paging services.
While current paging services providing paging involving transmission of pages between multiple switches have a distributed network of switches, they do not utilize the distributed switches to maximize the efficiency of transmission of pages within a local service area and outside of the local service area. These systems control the transmission of pages between switches by sorting of the pages at the originating central switch where the subscriber file is located. The pages are not further sorted and packetized during their transmission at intermediate switches located between the originating central switch and the destination switch which limits the efficiency of transmission that could be achieved by a system in which the pages at intermediate switches are sorted, buffered and combined with new pages that originate at the intermediate switches that are to be transmitted toward the destination switch to minimize the cost of transmission to a destination switch. Furthermore none of these systems permits pages to be entered by the local switch into the switching network while bypassing the central switch because of the fact that subscriber information is centrally stored and must be centrally processed.
The central processing of pages by existing systems has distinct disadvantages. First, expansion of the capacity of the network is limited by the capacity of the central switch to process all requests for pages. Since studies of the assignee reveal that a majority of pages (70%) originating at a local paging facility are typically intended for only the broadcast by a single local paging facility, central processing of a page to be broadcast by a single local paging service necessarily places a high processing overhead on the central processor's ability to process pages which are to be transmitted between switches (i.e., non-local paging) and necessitates the making of a long-distance or 800 phone call. Furthermore, the cost of expanding the capacity of a central processing facility to increase the volume of pages can involve substantial expense. Finally, a malfunction in the central processing system processing the requests for pages throughout the network can cause the whole network to go down.
Each paging receiver in the Metrocast system cyclically scans a plurality of closely spaced channels to detect the presence of a page addressed to the paging receiver on any one of the closely spaced channels. Paging receivers in the Metrocast system have the disadvantage that the required continual scanning of the closely spaced channels consumes a substantial amount of power causing the batteries of the paging receiver to have a short service life. Short battery life increases the cost of operation of the paging receiver, can cause pages to be lost when the batteries are not promptly replaced and can interfere with the ability to market paging services as being "economical" given the cost of battery replacement.
There currently is no universal standard for issuing identification numbers to paging receivers, with the largest system having capacity for issuing only 2,000,000 paging receiver identification codes. Worldwide, there currently are over 12,000,000 paging receivers in use with projected growth on an annual basis in the paging industry possibly exceeding 20%. Thus, current paging systems do not permit a worldwide paging system to be realized as a result of the actual and projected number of paging receivers being far larger than the capacity of the identification codes in the largest existing paging system.
All paging receivers currently consume considerable battery power in monitoring the one or more channels on which they are designed to receive pages to detect if a paging receiver identification code accompanying a page on the one or more channels matches its stored paging receiver identification code. If a match exists, then a page is processed and an alarm and a display of the message is provided by the paging receiver of the message contained with the page. These systems transmit the paging receiver identification code in an order of decreasing significance of the digits of the identification code. In other words, if a paging receiver has the identification code 12345, the transmitter precedes the transmission of the page which is addressed to the paging receiver with the sequence of digits 12345. Each paging receiver which receives the channel on which the paging receiver identification code is transmitted continually detects each of the successive digits and maintains its radio frequency receiver tuner in any "on" state until a mismatch is found between the transmitted and stored paging receiver identification code digits. As a result of the fact that many paging receivers have the most significant digits in common with other paging receivers within a system, a substantial amount of battery power is consumed detecting if a broadcast page is addressed to a particular paging receiver. Each paging receiver which receives the digits of the paging receiver identification code in an order of decreasing significance is statistically likely to have its radio frequency receiver turned on for most of the transmission of the digits of the paging receiver identification code until the lesser significant digits of the paging receiver identification code are received which enable a final determination to be made of the paging receiver to which a page on a frequency is addressed. The lesser significant paging receiver identification code digits are the digits which begin to distinguish one paging receiver from another and only the least significant paging receiver identification digit distinguishes the paging receiver which is desired to receive a particular page from all other paging receivers. Accordingly, the transmission of the paging receiver identification code digits in an order of decreasing significance substantially increases power consumption lessening the life of the batteries of the paging receivers in a system.
Throughout the world, different frequency bands have been adopted for transmitting pages. In the United States, transmissions are authorized on VHF and UHF bands. In the United States, the channels of the VHF and UHF bands are separated by 5 KHz steps. Moreover, for each of these bands in the United States, transmitters are in existence which transmit pages by frequency modulation of a digitally encoded carrier wave and other transmitters which transmit pages by frequency modulation of an analog encoded carrier wave. Currently, no paging receiver exists which is compatible with transmissions from both analog and digital transmitters. Furthermore, Europe has allocated VHF channels for paging with individual channels being separated by 6.25 KHz steps and Far Eastern countries have allocated paging frequencies on a 280 MHz VHF band with individual channels being separated by 2.5 KHz steps. Currently, paging receivers do not exist which are operational on any more than one of the above-identified frequency bands. The inability of current paging receivers to receive pages on the different frequency bands allocated throughout the world effectively prevents worldwide paging to be received on a single paging receiver.
None of the existing paging systems dynamically change the channels on which a paging receiver in the system may receive pages which severely restricts the paging receivers to usage in limited geographical areas. In the United States, there are a large number of paging in use in different geographical parts of the country. Because of the fact that the channel reception channels of existing paging receivers are not dynamically changed, it is impossible to universally receive pages throughout the country to offer special services, or to shift allocation of channels used by a local paging service to accommodate traffic variations because of the fact that reception of channels in current systems is limited to a single channel frequency fixed upon obtaining the paging receiver from the paging service or to cyclically scan a group of closely spaced channels such as with the paging receiver used by the Metrocast system. The prior art paging receivers' inability to dynamically change the channels which may be received severely limits the usage of paging for business or other travel.
Currently, no paging system exists which effectively and at low cost permits paging on a regional, national and international level. This is a consequence of the inability of the paging receivers to dynamically receive different and a large number of channels, the lack of a standard transmission protocol which is compatible with existing analog an digital transmitter hardware and existing systems not having a universal paging receiver identification code which uniquely identifies each of the paging receivers throughout the world. The possibility exists in the current systems of several pager having the same paging receiver identification code. Furthermore, the architecture of existing systems is committed to the construction of dedicated communication links between switches and/or the construction of new broadcast facilities such as at the local switches which involves substantial capital expenditures. A universal paging receiver identification code is needed having the capacity to uniquely identify all of the paging receivers throughout the world. Furthermore, in order to inexpensively implement regional, national and international paging, a system is needed which utilizes existing local paging services without expenditures on communication links between switches or new broadcast facilities.
Currently in the United States, a relatively small number of channels are used in the large metropolitan areas where most of the paging traffic occurs. As paging traffic increases in view of the relatively small number of channels predominantly in use in metropolitan areas, there is the likelihood that message traffic during the three peak paging periods that occur each day will increase to the point where the predominantly used small number of channels will become so busy that it is impossible to rapidly transmit pages to a paging receiver. This condition has occurred in large metropolitan areas and results in delays in pages being transmitted during peak traffic periods. Because of the fact that current paging receivers are not dynamically programmable to receive pages on different channels, existing networks do not have the ability to dynamically switch channels in large metropolitan areas from a channel having the highest traffic to a channel or channels having lower traffic, to accommodate paging traffic variations when one channel becomes so busy that rapid paging is not possible. In fact, in large metropolitan areas, there currently are VHF and UHF mobile channels that are under-utilized due to the current cellular radio system which could be used as alternative paging channels to receive traffic on commonly used stations.
Distinct FM analog and FM digital paging encoding protocols exist, but no universal encoding protocol exists which may be transmitted by existing analog and digital FM paging transmitters and universally received by paging receivers. Existing protocols for the FM analog and digital paging systems do not have a high efficiency in transmitting data per transmitted code. Existing digital transmitters modulate a digital FM transmitter with a binary signal which utilizes frequency shift keying of the basic carrier signal to transmit the high level of a bit with a burst of the shifted frequency and the low level of a bit with the unshifted frequency of the carrier. Thus, each identifiable digit of the transmission from an FM digital paging transmitter can encode only two distinct levels for each frequency burst of the carrier. Analog FM paging transmitters frequency modulate a sinusoidal carrier with a total of 15 tones to create a hexadecimal value level transmitting system in which no modulation of the basic carrier frequency is considered to be the "F" value and the remaining 15 different values are encoded by modulating the FM carrier with distinct tones. Paging receivers which are designed to receive analog transmissions require substantial reception time of each ton to validly detect each character. Thus, while the protocol of FM analog paging transmitters transmits a much higher number of data values for each frequency burst, the slowness of the paging receivers in detecting the discrete tones does not result in a high throughput speed of transmitting characters.
Prior art alphanumeric paging (the capability of transmitting pages having numerical and alphabetic type characters) has been commercialized using the above-referenced digital encoding protocol. Since only about 15% of existing paging services use a digital transmitter, which is necessary currently for implementing alphanumeric paging, the great majority of subscribers to paging services may not obtain alphanumeric paging. The analog protocol, which is based upon a hexadecimal tone encoding format, has not been utilized for encoding a character set to transmit alphanumeric messages.
Moreover, current alphanumeric paging service has been expensive to implement both from the perspective of the paging service and from the subscriber. The necessary input devices have proved to be expensive and there is no standard input device design or data encoding protocol. Conversion equipment for changing an analog paging service to a digital service with alphanumeric capability has proven expensive and there is no existing computer system for changing an analog system to a digital system which is inexpensive.
Existing paging systems which permit paging in multiple locations have the deficiency when a subscriber desires to place a page from a location remote from the subscriber file or to modify the level of service from a location remote from the subscriber file of requiring a long-distance phone call to be made to the location where the subscriber file exists. Because of the fact that the long-distance phone call is charged to the person wishing to make the page or change of service level or to the operator of the system (800 service), the expense of using these paging systems is increased and may discourage users from making pages or changes in the level of service by calling in from a location remote from the subscriber file. No national or regional prior art paging system permits a page or a change in service level to be initiated from a geographic area outside the area where the subscriber file is located by making a local phone call to a switch in an area remote from the switch containing the subscriber file within the system and further for the paging receiver to be programmed to receive the page on a particular channel used at the location where the page is to be received.
Current paging systems do not broadcast and current paging service receivers do not execute a repertoire of commands permitting the functional characteristics of the paging receiver to be programmed dynamically by RF transmission to the paging receiver. Current paging receivers do respond to commands which provide an alarm to the person wearing the paging receiver that a page has been received such as activating a display and/or providing an audio alarm. However, current paging systems do not broadcast and current paging receivers do not execute a diversity of commands in which the system influences operation and structure of the paging receiver, including commands activating the display to indicate if the page has originated locally or from another region, causing the message transmitted with the page to be stored in a particular memory location in the paging receiver, programming the channels on which the paging receiver is to receive pages, and permitting the paging receiver to serve as a relay for pages either to be transmitted or received and to interface with peripheral devices.
Cellular radio systems dynamically assign channels on which cellular radio receivers are to receive telephone calls. To make or receive a telephone call, a mobile cellular radio is locked onto a set up channel through communications with the transmitter which are established when the cellular radio receiver is turned on. The cellular system then assigns the mobile cellular radio to a specific channel while the mobile cellular radio is making or receiving a telephone call within a cell. As the cellular radio receiver moves from one cell to another cell, the channel is dynamically changed from one channel to another channel to maintain a strong signal frequency. A cellular radio receiver does not have a channel memory which stores channels which are to be scanned to establish if a call is forth coming. The dynamic assignment of a channel is initiated by the transmitter for the sole purpose of establishing the channel over which voice communications are to be initiated or to be maintained when moving from one cell to another. Cellular radio systems do not assign channels based upon information assigned in a subscriber file.
The telephone system is based upon a network of distributed switches having a local/regional/national/international functional responsibility. In the United States local telephone offices are connected to "lata" switches which are analogous to area codes but which are identified by a different number pattern based upon system considerations. The local, lata, and hub switches of the present invention operate in a fundamentally different manner than the switches of the telephone system in that they perform substantial data processing to provide packets of data which are periodically transmitted to other switches to provide efficient and low cost operation. The operation of the telephone system is fundamentally different from a paging system in that processing of calls in the telephone system is on a real-time basis which does not process calls to provide packets which are periodically transmitted and in that the initiation of a successful call requires the caller to know the destination of the call (phone number), neither of which occurs in a paging system.
A network known as ISDN (Integrated Service/Digital Network) has been proposed. This network will interface with the telephone system and provide data communications between switches in the network. Data is to be transmitted in blocks between switches in the network. The proposal does not include disassembly, processing and reassembly of blocks of data by intermediate switches located along the communication path between an originating and destination switch.
The X.25 transmission protocol has been developed which is used for sending a single block of data between an originating location and a receiving location. The prior art X.25 transmission protocol is identical to that discussed with reference to FIG. 29 except that it has not been used in paging and further has not been used for transmitting multiple blocks of data analogous to the multiple pages illustrated therein.
U.S. Pat. No. 4,422,071 discloses a system for programming an identification code of a receiver by a radio frequency communication between a transmitter and the receiver.